This research project aims at a better understanding of the molecular structure of nerve and photoreceptors. This research is in the field of biophysics and uses primarily x-ray diffraction methods. The nerve and photoreceptor specimens are maintained in a living condition during the x-ray diffraction experiment. A variety of nerves and photoreceptors are to be studied. The x-ray diffraction data will be suitably processed and the structure analysis will then provide an electron density description in a direction at right angles to the membrane surface. The immediate objective is to obtain the electron density description at moderate to high resolution. An attempt will be made to derive the electron density profile using direct methods of analysis so that the derived profile can be shown to be correct. Experiments to obtain an accurate absolute electron density scale are planned. The molecular distribution of the nerve and disc membranes will be studied. The aim here is to assemble the molecular components of the membrane in such a way that the resulting molecular model will have an electron density distribution in agreement with the derived electron density profile. It is anticipated that this research will contribute new information relating to the problem of nerve conduction and to the biophysics of vision.